The objectives of this undertaking are to originate new epidemiologic approaches to the study of cancer causation in man, to develop sources of data related to specific epidemiologic problems, and to stimulate epidemiologic research in other health agencies. Opportunities for research in cancer epidemiology are based on questions arising from clinical or laboratory observations, on unusual groupings of cancer cases in the population, and on study of the characteristics of groups of persons prior to the onset of a specific type of cancer as compared with similar persons who have not developed the disease.